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Budi Purnama,Rafika Rahmawati,Agung Tri Wijayanta,Suharyana 한국자기학회 2015 Journal of Magnetics Vol.20 No.3
Modifications in the structural and magnetic properties of co-precipitated cobalt ferrite nanoparticles can be accomplished by varying the annealing time periods during the synthetic process. Experimental results show that high-purity cobalt ferrite nanoparticles are obtained using a co-precipitation process. The dependence of the crystallite sizes on the annealing time was successfully demonstrated using XRD and SEM. Finally, vibrating sample magnetometer analyses show that the magnetic properties of the cobalt ferrite nanoparticles depend on their relative particle sizes.
Budi Purnama,Anisa Khoiriah,Suharyana 한국자기학회 2018 Journal of Magnetics Vol.23 No.1
The crystal structure and magnetic properties of aluminium-substituted cobalt-ferrite nanoparticles synthesised by the co-precipitation are reported in this study. The single phase nanoparticles are obtained. Magnetic property Changes in these properties are clarified mainly by changes in parameters such as the crystalline constant, crystallite size and crystalline density. An increase of saturated magnetisation with annealing temperature is also observed. Results for the change in saturated magnetization at several elevated temperatures indicate that the available non-magnetic aluminium ions support redistribution of cation-trivalent Fe<SUP>3+</SUP> during the annealing process at octahedral sites.
Retna Arilasita,Utari,Budi Purnama 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.74 No.5
This study aims to prepare strontium-substituted cobalt ferrite (Sr$_{0.1}$Co$_{0.9}$Fe$_2$O$_4$) nanoparticles by using a simple co-precipitation process followed by annealing at 300$^\circ$C--600$^\circ$C for 5 h. The Sr$_{0.1}$Co$_{0.9}$Fe$_2$O$_4$ nanoparticles thus obtained have a face-centred cubic (fcc) inverse-spinel crystalline structure with crystallite sizes in the range from 17.26 to 26.97~nm. The saturated magnetization of the nanoparticles increases with increasing annealing temperature. Furthermore, the transition from a multi-domain to a single-domain configuration is investigated from the viewpoint of the dependence of the crystallity on the coercive field.
Arilasita Retna,Utari,Purnama Budi 한국물리학회 2021 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.79 No.2
We report change in the structural and the magnetic properties of a gamma-irradiated sample of CoBi0.1Fe1.9O4 nanoparticles synthesized using the co-precipitation method. All samples were exposed to low doses of γ-radiation (i.e., 0, 100, 200, 400, and 800 Gy). The X-ray diffraction (XRD) evaluations indicated that all samples had a single-phase cubic spinel structure in space group Fd3m. The crystal size, lattice parameter, and other structural parameters of the irradiated CoBixFe2- xO4 nanoparticles were calculated based on the XRD data. The crystallite size is found to increase with increasing radiation dose. The stretching vibration modes of the absorption bands (v1 and v2) were observed in the Fourier transform infrared (FTIR) spectrum, thereby reconfirming that the metal oxide is realized a cobalt ferrite-based material. The change in the surface morphology was measured using scanning electron microscopy (SEM). Finally, the modified magnetic parameters (Hc, Ms, Mr) of the gamma-irradiated samples were determined from the M–H loop recorded at room temperature.
Evangelin Hutamaningtyas,Utari,Suharyana,Budi Purnama,Agung Tri Wijayanta 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.69 No.4
The effects of the synthesis temperature on the crystalline structure and the magnetic properties of cobalt ferrite (CoFe2O4) nanoparticles prepared via coprecipitation are discussed. The synthesis was conducted at temperatures of 75 C, 85 C and 95 C. Fourier transform infrared spectroscopy characterization related to a stretching vibration at a wavenumber of 590 cm−1 indicated the formation of a CoFe2O4 metal oxide. In addition, powder X ray diffraction (XRD) characterization proved that the metal oxide was CoFe2O4. Crystallite sizes calculated using the Scherer formula at the strongest peak of the XRD spectra of the samples synthesized at 75 C, 85 C and 95C were 32 nm, 43 nm and 50.4 nm, respectively. Finally, the results of the vibrating sample magnetometer characterization showed that the saturation magnetization decreased with increasing synthesis temperature, which is related to the dominant preference of Co2+ over Fe3+ cations at the octahedral sites.
Low Writing Field on Perpendicular Nano-ferromagnetic
Nur Aji Wibowo,Ferdy S Rondonuwu,Budi Purnama 한국자기학회 2014 Journal of Magnetics Vol.19 No.3
For heat-assisted magnetic recording, magnetization reversal probabilities of nano-Pt/MnSb multilayer film with perpendicular magnetic anisotropy under thermal pulse activation were investigated numerically by solving the Landau-Lifshift Gilbert Equation. Magnetic parameters of nano-Pt/MnSb multilayer were used with anisotropy energy of 3 × 10<SUP>5</SUP> erg/cc and saturation magnetization of 2100 G, which offer more than 10 y data stability at room temperature. Scheme of driven magnetic field and thermal pulse on writing mechanism was designed closely to real experiment. This study found that the chosen material is potential to be used as a high density magnetic storage that requires low writing field less than two-hundreds Oersted through definite heating and cooling interval. The possibility of writing data with a zero driven magnetic field also became an important result. Further study is recommended on the thickness of media and thermal pulse design as the essential parameters of the reversal magnetization.